Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754251Ab0LOOTG (ORCPT ); Wed, 15 Dec 2010 09:19:06 -0500 Received: from thoth.sbs.de ([192.35.17.2]:24393 "EHLO thoth.sbs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752839Ab0LOOTF (ORCPT ); Wed, 15 Dec 2010 09:19:05 -0500 Message-ID: <4D08CE44.6000407@siemens.com> Date: Wed, 15 Dec 2010 15:18:44 +0100 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: Thomas Gleixner CC: Jan Kiszka , Avi Kivity , Marcelo Tosatti , "linux-kernel@vger.kernel.org" , kvm , Tom Lyon , Alex Williamson , "Michael S. Tsirkin" Subject: Re: [PATCH v3 2/4] genirq: Inform handler about line sharing state References: <4D07F70A.30209@web.de> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1564 Lines: 43 Am 15.12.2010 14:04, Thomas Gleixner wrote: > On Wed, 15 Dec 2010, Jan Kiszka wrote: >> Am 14.12.2010 21:54, Thomas Gleixner wrote: >>> On Mon, 13 Dec 2010, Jan Kiszka wrote: >>>> @@ -943,6 +950,9 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id) >>>> /* Make sure it's not being used on another CPU: */ >>>> synchronize_irq(irq); >>>> >>>> + if (single_handler) >>>> + desc->irq_data.drv_status &= ~IRQS_SHARED; >>>> + >>> >>> What's the reason to clear this flag outside of the desc->lock held >>> region. >> >> We need to synchronize the irq first before clearing the flag. >> >> The problematic scenario behind this: An IRQ started in shared mode, >> this the line was unmasked after the hardirq. Now we clear IRQS_SHARED >> before calling into the threaded handler. And that handler may now think >> that the line is still masked as IRQS_SHARED is set. > > That should read "not set" I guess. Can't remember who wrote this, but that guy might have been too tired for clear sentences: Yes, of course, we could run into troubles, if IRQS_SHARED was _not_ set while the IRQ line is unmasked between hard and threaded handler. > Hmm, needs more thoughts :( Be warned, might be painful. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/